1. Field of the Invention
The present invention relates to a driving apparatus including a joint member which connects a driving shaft with a driven shaft so that torque is transmitted from the driving shaft to the driven shaft while absorbing the eccentricity between both shafts, and to a driving apparatus which is employed as a driving apparatus of a position adjusting mechanism for a steering device or a seat device.
2. Description of the Prior Art
A conventional driving apparatus of this kind is disclosed, for example, in Japanese Patent Laid-Open Publication No. 63(1988)-34252. This driving apparatus includes a driving shaft rotated as an output shaft of a motor, a driven shaft which is connected with the driving shaft and on which a worm-gear is fixed, a joint member which connects the driving shaft with the driven shaft so that torque is transmitted from the driving shaft to the driven shaft while absorbing the eccentricity between both shafts. Furthermore, this driving apparatus includes a first groove portion formed on the joint member, a first wall portion formed on the driving shaft and fitted into the first groove portion so as to be able to move in the diametrical direction and engaged with the first groove portion, a second groove portion formed on the joint member so as to meet with the first groove portion at a right angle and a second wall portion formed on the driven shaft and fitted into the second groove portion so as to be able to move in the diametrical direction and engaged with the second groove portion. Thereby, the eccentricity between the driving shaft and the driven shaft is absorbed by the movement of the first and second wall portions of the diametrical direction in regard to the first and second groove portions, respectively. Simultaneously, the torque is transmitted from the driving shaft to the driven shaft via the engagement between the first and second wall portions and the first and second groove portions, respectively.
In the above conventional driving apparatus, however, since a predetermined clearance is formed between the first and second wall portions and the first and second groove portions so that the first and second wall portions are able to move in the diametrical direction in regard to the first and second groove portions, respectively, a vibration is generated between the driving shaft and the joint member and between the driven shaft and the joint member by the clearance, respectively. Thereby, there is a danger an uncomfortable noise and so on is caused by the vibration.